Which statement describes the effect of increased potassium influx on neurons during opioid receptor signaling?

Which statement describes the effect of increased potassium influx on neurons during opioid receptor signaling?

• A. Hyperpolarization and reduced excitability
• B. Depolarization and increased excitability
• C. No change
• D. Increased conduction velocity

Answer: (A)

Opening potassium channels is the key effect of opioid receptor signaling in neurons. When these receptors (Gi/o coupled) are activated, they cause GIRK-type potassium channels to open, increasing potassium conductance. Potassium tends to move out of the cell along its electrochemical gradient, driving the membrane potential toward the potassium equilibrium potential and making the inside more negative. That hyperpolarization raises the threshold for triggering an action potential, so the neuron becomes less excitable and less likely to fire. In addition, opioid signaling also reduces calcium influx by inhibiting voltage-gated calcium channels, which further decreases neurotransmitter release. The combined result is hyperpolarization with reduced neuronal excitability, which aligns with the described effect. The notion of increased potassium influx would not produce hyperpolarization, since outward K+ movement (not inward) is what hyperpolarizes the membrane in this context.

Opening potassium channels is the key effect of opioid receptor signaling in neurons. When these receptors (Gi/o coupled) are activated, they cause GIRK-type potassium channels to open, increasing potassium conductance. Potassium tends to move out of the cell along its electrochemical gradient, driving the membrane potential toward the potassium equilibrium potential and making the inside more negative. That hyperpolarization raises the threshold for triggering an action potential, so the neuron becomes less excitable and less likely to fire.

In addition, opioid signaling also reduces calcium influx by inhibiting voltage-gated calcium channels, which further decreases neurotransmitter release. The combined result is hyperpolarization with reduced neuronal excitability, which aligns with the described effect. The notion of increased potassium influx would not produce hyperpolarization, since outward K+ movement (not inward) is what hyperpolarizes the membrane in this context.